Catalytic Impact of Clays During In-Situ Combustion
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AbstractClays are known to act as a catalyst during the in-situ combustion (ISC) process. This work investigates the role of clay in reaction kinetics of a bitumen sample.Several Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) experiments were conducted on a Canadian bitumen and its saturates, aromatics, resins, and asphaltenes (SARA) fractions in the presence and absence of a clay (kaolinite and illite) mixture. The role of each fraction in ISC reactions was investigated at low temperature oxidation (LTO) and high temperature oxidation (HTO) regions by calculating the total activation energy and the heat of combustion. The activation energy calculations were based on the Arrhenius approximation and the heat of reaction was estimated by a simple integration of the DSC curve below the standard zero heat generation line.Accordingly, we have observed that saturates act like ignitors and their ignition characteristics are enhanced in the presence of clay. Bitumen oxidation in LTO region requires more heat for asphaltenes only in the absence of clay. In the presence of clays, bitumen oxidation in LTO region requires more heat for the mutual interaction of resins with asphaltenes. The required heat for the bitumen oxidation and combustion in HTO region is reduced due to contribution of mainly saturates fraction in the presence of clays. The generated heat (heat of combustion) is increased both in LTO and HTO regions for clay presence case. This is mainly due to the mutual interaction of aromatics fraction with resins fraction in LTO region and the mutual interaction of aromatics fraction with saturates fraction in HTO region. It has also been found that bitumen sample contains emulsified water, which reduces the combustion process performance.
